Is nuclear power safe?
Short answer: No.
Slightly longer answer: Neither is anything else.
There is no such thing as perfectly safe ANYTHING. It’s always a matter of weighing the costs vs. the benefits. The fundamental rule of analysis is always to ask “Compared to what?”.
Notice that, for all the attention paid to the Fukushima Daiichi reactor, hardly anybody at all noticed the earthquake-induced dam collapse, with the resultant downstream devastation caused when all the pent-up water went rushing to the sea. That was something that ACTUALLY HAPPENED with supposedly “safe” hydroelectric power, not something that MIGHT YET HAPPEN with nuclear.